Can’t Connect Online – Issue Fix
If you can’t get FIFA 21 to connect online, Electronic Arts suggests a few ways to make it possible. First, flush your DNS through the Command Console with the line ipconfig/flushdns. Close any background programs and run the game as an administrator. Check if that works.
If it doesn’t then, you can try rebooting your PC and your internet connection as residue from closed programs could be refraining FIFA 21 from connecting.